Aug.17 (GMM) Michael Schumacher's manager has hit back after Alain Prost suggested the 40-year-old's neck injury might not be the only reason he called off his F1 comeback.

"It remains to be seen if Schumacher stopped solely because of the health problem, or because when he resumed driving he realised the task was enormous," Frenchman Prost, a winner of four titles, told the Le Parisien newspaper.

Following two weeks of hype and excitement, German Schumacher announced last week that he will no longer replace Felipe Massa at forthcoming races due to the lingering effects of a motorcycle testing fall earlier this year.

But Prost, 54, said the full truth of Schumacher's u-turn may be different.

"The body changes very quickly when you stop racing," said Prost, who had a sabbatical in 1992 and then returned to win his last title in F1 the following season.

"A driver does not react the same way and the vision is not as sharp. When I returned in 1993 after eight months out it was very difficult to find the best level.

"In 1994 McLaren asked me to take the wheel. I conducted three days of testing and I immediately realised something in me was broken.

"The speed was there but not the will to manage the pressure, travel and media that comes with a championship contest," he explained.

Schumacher's manager Willi Weber rubbished Prost's hypothesis in the pages of the German newspaper Bild.

"Unfortunately I have to disappoint Mr Prost. Michael's (lap) times at his test (in the 2007 car) at Mugello told a very different story.

"The decision (to not return) was only because of his neck problems," Weber insisted.